Good thing restricting side-loading isn't legal in the European Union! Not a problem here. Apple had to enable side-loading on their EU-based phones and so will Google if they restrict it.
So I'm leaning more towards Apple is in compliance and the common perception is incorrect. Which is fairly common when it comes to laws and regulations of any country.
While MS code signing certs are more circumventable for power-users than Android's new approved developer program, their pricing is far more prohibitive for independent OSS developers and hobbyists, costing hundreds of USD per year.
Not even playing devil's advocate, just wondering how many loopholes actually exist.